Journal of Pain Research
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ORIGINAL RESEARCH
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Pain extent and function in youth with physical disabilities This article was published in the following Dove Press journal: Journal of Pain Research 5 January 2017 Number of times this article has been viewed
Jordi Miró 1–4 Rocío de la Vega 1,5 Catarina Tomé-Pires 1–3 Elisabet Sánchez-Rodríguez 1–3 Elena Castarlenas 1–3 Mark P Jensen 5 Joyce M Engel 6 1 Unit for the Study and Treatment of Pain – ALGOS, Universitat Rovira i Virgili, Catalonia, Spain; 2Research Center for Behavior Assessment (CRAMC), Department of Psychology, Universitat Rovira i Virgili, Catalonia, Spain; 3Institut d’Investigació Sanitària Pere Virgili, Catalonia, Spain; Universitat Rovira i Virgili, Catalonia, Spain; 4Chair in Pediatric Pain, Universitat Rovira i VirgiliFundación Grünenthal, Catalonia, Spain; 5Department of Rehabilitation Medicine, University of Washington, Seattle, WA, USA; 6Department of Occupational Science and Technology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
Background: The aim of this study was to increase our understanding of the role that spatial qualities of pain (location and extent) play in functioning, among youths with disabilities and chronic pain. Methods: One-hundred and fifteen youths (mean age 14.4 years; SD ±3.3 years) with physical disabilities and chronic pain were interviewed and were asked to provide information about pain locations and their average pain intensity in the past week, and to complete measures of pain interference, psychological function and disability. Most of the participants in this sample were males (56%), Caucasian (68%), and had a cerebral palsy (34%) or muscular dystrophy (25%) problem. Most participants did not report high levels of disability (X =12.7, SD ±9.5, range 0–60) or global pain intensity (X =3.2, SD ±2.4, range 0–10). Results: Pain at more than one body site was experienced by 91% of participants. There were positive associations between pain extent with pain interference (r = 0.30) and disability (r = 0.30), and a negative association with psychological function (r = –0.38), over and above average pain intensity. Additionally, pain intensity in the back (as opposed to other locations) was associated with more pain interference (r = 0.29), whereas pain intensity in the shoulders was associated with less psychological function (r = –0.18), and pain intensity in the bottom or hips was associated with more disability (r = 0.29). Conclusion: The findings support the need to take into account pain extent in the assessment and treatment of youths with physical disabilities and chronic pain, call our attention about the need to identify potential risk factors of pain extent, and develop and evaluate the benefits of treatments that could reduce pain extent and target pain at specific sites. Keywords: pain extent, pediatric chronic pain, physical disability, function
Background
Correspondence: Jordi Miró Departament de Psicologia, Universitat Rovira i Virgili, Carretera de Valls s/n, 43007 Tarragona, Spain Telephone: +34 9 775 5179 Email [email protected]
A growing body of evidence indicates that chronic pain is a significant problem for adults with physical disabilities.1–4 Moreover, although information from pediatric populations is scarce, research indicates that chronic pain is also a relevant health issue in youth with physical disabilities.5,6 For example, recent studies have shown that pain intensity significantly and negatively impacts the physical, emotional, and social function of youth with disabilities.7–9 The experience of pain involves more than just pain intensity; pain is a multidimensional construct that has spatial (ie, the location[s] and overall extent of perceived pain), temporal (eg, constant vs intermittent, acute vs chronic), and quality (eg, hot, electrical) characteristics. Research has shown that function, at least in adults with physical disabilities, is influenced by some of these other pain characteristics over 113
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Journal of Pain Research 2017:10 113–120
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© 2017 Miró et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php).
http://dx.doi.org/10.2147/JPR.S121590
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Miró et al
and above the effects of pain intensity. For example, pain at certain locations, such as the head in adults with myotonic and facioscapulohumeral dystrophy10 or in the low back and legs in adults with spinal cord injury,11 has been demonstrated to be of greater importance than pain in other body locations in the function of these individuals. Similarly, pain extent – the total number of body areas where pain is experienced – has been found to be associated with function over and above the effects of global pain intensity in adult populations with physical disabilities and chronic pain.4 That is to say, adults who report more than one distinct pain problem or pain in more body locations are likely to also report poorer quality of life and worst function than those with pain in just one location, even when controlling for pain intensity. Similar findings have been reported in studies using samples of individuals with chronic pain as a primary presenting problem.12–15 However, the role that the spatial qualities of pain play in the function of youth populations with chronic pain is very limited. To the best of our knowledge, just one study with young people with chronic pain has addressed this issue. In this study, de la Vega et al7 reported a significant negative association between pain extent and sleep quality in a sample of 414 adolescents and young adults with a variety of chronic pain problems. Aili et al16 also reported an association between disturbed sleep and multi-site pain in a longitudinal study with a sample of individuals with low back pain. However, although they studied adults, their sample included individuals 20–59 years old, and so it is unclear how many of their sample were aged in their early twenties, and could therefore be regarded as young people. Although it is reasonable to hypothesize that additional research in samples of youth would replicate these very preliminary results regarding the importance of pain location and pain extent, further research to establish the reliability of the findings regarding pain site and extent in youth is needed, as children should not be viewed simply as little adults.17 In fact, investigators have called for more research to study the occurrence and impact of multi-site pain in young people, as a way to identify factors that may play a role in the impact of chronic pain in youths.12 Such information is critical in order to better understand if and how adults and youth are different with respect to the key aspects that are relevant in the function of individuals with disabilities and chronic pain. If pain extent is found to contribute to the prediction of function among youth with physical disabilities and chronic pain – particularly if it does so over and above the effects of overall pain intensity – this would help us to better understand who might be at most risk of
114
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worse adjustment, and therefore who might benefit the most from treatments designed to help youth with disabilities adjust to chronic pain. Furthermore, the findings from such research would also be relevant to clinicians who design specific treatment programs, and to examine and compare the results of treatments tailored to the specific needs of the patients. For example, the hypothesis that patients with chronic localized pain in the low back would respond better to physical therapy whereas those with more extended multi-site pain problems may gain the greatest benefit from cognitive behavioral therapy,18 could be tested. Given these considerations, the aim of this study was to increase our understanding of the role that pain extent plays in function among youth with disabilities and chronic pain. On the basis of previous research with adults, we hypothesized that pain extent would demonstrate a unique positive association with pain interference, and negative associations with psychological function and disability when controlling for average pain intensity. We also sought to examine the role that individual pain sites (eg, low back pain vs headache) might play in the associations between pain intensity and function, although we did not set a priori hypothesis regarding the importance of one pain site over another, given the paucity of previous research on this topic.
Methods Participants Participants came from a convenience sample of 115 young people with physical disabilities who had participated in a longitudinal study about the impact of chronic pain secondary to a physical disability. Although a number of articles have been published using data from this survey,19–22 none of the previous articles have addressed the study questions that are the focus of the current analyses. In order to participate in the original study, potential participants needed to: 1) have a chronological age from 8 to 21 years; 2) have a diagnosis of cerebral palsy, neuromuscular disease, spinal cord injury, spina bifida, or limb deficiency (acquired or congenital); 3) be able to understand and speak English; 4) have no more than mild cognitive impairment (as measured by the modified version of the Mini-Mental State Examination);23 and 5) have the capacity for expressive communication which might have included the use of augmentative communication devices. In addition, participants for the current analyses had to report that they were experiencing a bothersome pain problem (other than one associated with a minor acute injury or illness) in the 3 months prior to the interview. We did not limit participants
Journal of Pain Research 2017:10
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to children (ie, age ≤18 years), because many pediatricians continue to treat patients that they have a history of treating, even after they become 18 years old. In fact, this study was addressed to youth, a group that normally includes individuals in their twenties.
Procedures Further details on the study procedures can be found in the original study.22 Briefly, and most germane to the current study, participants were enrolled from different sources and with different techniques including word of mouth, mailings from clinics, and contacts with a summer camp sponsored by the Muscular Dystrophy Association (USA). Written, informed consent was obtained from all participants or their legal guardian if a minor. Following study enrollment, both youth participants and one of their parents or legal guardians were interviewed in person (when possible) or via telephone. The study was approved by the Institutional Review Board at the Children’s Hospital and Regional Medical Center (Seattle, WA, USA).
Measures The parents of the youth participants in the original study were administered a structured interview that requested information about their child’s age, sex, and medical diagnosis. The youth participant interviews included questionnaires and rating scales assessing pain and disability, as well as psychological and physical functioning domains.
Pain intensity Pain intensity was measured with a 0–10 numerical rating scale (NRS-11). Participants were asked to rate their average pain intensity in the past week by choosing a single whole number between 0 (“No pain”) and 10 (“Pain as bad as could be”) that best represented that pain. The NRS-11 has been found to be valid and reliable when used with young people24 even when used with children as young as 6 years of age25,26 and with young people with physical disabilities.21
Pain site and extent The youth participants were also asked to indicate in which of 12 body location categories (that included 11 specific locations as well as an “other” category) they experienced pain as well as the intensity of the pain at each one of those locations. The 12 locations were: head, neck, chest, shoulders, back, arms, hands, bottom/hips, belly/pelvis, legs, feet, and “other”. The number of locations were summed to create the pain extent score for each participant (possible range: 1–12). Journal of Pain Research 2017:10
Pain extent and function
Pain interference We used a modified version of the Brief Pain Inventory (BPI)27,28 to assess pain interference. The modifications to the original 7-item questionnaire included: 1) adding three items that were specially relevant for this group of individuals with disabilities, and included items that assessed pain interference with “self-care (taking care of your daily needs)”, “recreational activities”, and “social activities”, thus increasing the content validity of the scale; 2) revising the interference with “walking” item to ask about interference with “mobility (ability to get around)” which made it possible for all of the participants – including those who are not able to ambulate independently – to respond to this item; and 3) the item requesting information about “normal work” was changed to request information about “school, work, or chores”, which was considered to be a more age appropriate item. Scores from the 10-item version of the BPI used in this study demonstrated excellent internal consistency, as indicated by a Cronbach’s alpha of 0.90.
Psychological functioning The 16-item Mental Health scale (MH) of the Child Health Questionnaire (CHQ-CF87) was used to assess psychological functioning.29 The CHQ–CF87 is an 87-item questionnaire that was designed to assess psychosocial and physical wellbeing in children aged between 5 and 8 years. The CHQ– CF87 is scored by first computing a raw score, and then transforming it to standardized scores, with higher scores indicating better psychological functioning. The scales in the CHQ–CF87 have demonstrated adequate psychometric characteristics in a number of samples of young people with physical and psychological diagnoses.29 Scores from the MH scale in this study demonstrated excellent internal consistency, as indicated by a Cronbach’s alpha of 0.88.
Disability Disability was assessed using the 15-item Functional Disability Inventory (FDI).30 Respondents were asked to rate how difficult it was for them to engage in regular activities in the last few days on a 0 (“No trouble”) to 4 (“Impossible”) scale.31 The FDI was developed specifically to assess disability in children, and has demonstrated excellent reliability and validity properties.30,32 Higher scores indicate more disability (possible range: 0 to 60). In the current sample, the internal consistency (Cronbach’s alpha) of the disability score was 0.81.
Statistical analyses We first computed descriptive statistics for the demographic and study variables to describe the sample. Next, submit your manuscript | www.dovepress.com
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115
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Miró et al
we examined the distributions of the study variables and computed variance inflation factors (VIF) for the study predictors to ensure that they met assumptions for the planned regression analyses.33 We also computed zero-order correlation coefficients between pain extent and the criterion variables. Finally, we performed three regression analyses – one for each of the criterion variables of pain interference, psychological function, and disability – to determine if pain extent and pain intensity at specific sites explained unique variance in the criterion variables. We entered average pain intensity in step 1 as a control variable. We then entered pain extent in step 2 in order to determine if it accounted for significant variance in the criterion variables, over and above pain intensity. In step 3, we entered pain intensity at each of 12 pain sites, stepwise, to determine if pain intensity at any one (or more) specific site(s) contributed to the prediction of the criterion variables when controlling for pain intensity and pain extent.
Results Sample and study variables description The majority of the study sample were White/Caucasian (68%) and males (56%). The average age of the participants when they completed the survey was 14.4 years (SD ±3.3; median 13 years; range 8–21 years). Sixteen (14%) of the participants were prepubescent (age ≤10 years), 32 (28%) were 11–12 years old, 36 (31%) were 13–15 years old, 31 (27%) were 16–18 years old, and 14 (12%) were 19–21 years old. Almost all participants experienced pain at more than one body site (91%). Additional descriptive information about the study sample and variables in the study are presented in Tables 1 and 2.
Assumptions testing All of the distributions of the study variables were adequately normal for the planned regression analyses (skewness range –1.05 to 1.46; kurtosis range, –1.07 to 1.32). In addition, all of the variance inflation factor statistics were all well below the standard cutoff value of 10 (range 1.07 to 1.42), indicating that multicollinearity would not bias the findings.33
Zero-order correlations between pain extent and pain interference, psychological functioning, and disability The zero-order associations between pain extent and the study criterion variables (pain interference, psychological functioning, and disability) were 0.47, –0.49, and 0.36 (all p
Dovepress open access to scientific and medical research
ORIGINAL RESEARCH
Open Access Full Text Article
Pain extent and function in youth with physical disabilities This article was published in the following Dove Press journal: Journal of Pain Research 5 January 2017 Number of times this article has been viewed
Jordi Miró 1–4 Rocío de la Vega 1,5 Catarina Tomé-Pires 1–3 Elisabet Sánchez-Rodríguez 1–3 Elena Castarlenas 1–3 Mark P Jensen 5 Joyce M Engel 6 1 Unit for the Study and Treatment of Pain – ALGOS, Universitat Rovira i Virgili, Catalonia, Spain; 2Research Center for Behavior Assessment (CRAMC), Department of Psychology, Universitat Rovira i Virgili, Catalonia, Spain; 3Institut d’Investigació Sanitària Pere Virgili, Catalonia, Spain; Universitat Rovira i Virgili, Catalonia, Spain; 4Chair in Pediatric Pain, Universitat Rovira i VirgiliFundación Grünenthal, Catalonia, Spain; 5Department of Rehabilitation Medicine, University of Washington, Seattle, WA, USA; 6Department of Occupational Science and Technology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
Background: The aim of this study was to increase our understanding of the role that spatial qualities of pain (location and extent) play in functioning, among youths with disabilities and chronic pain. Methods: One-hundred and fifteen youths (mean age 14.4 years; SD ±3.3 years) with physical disabilities and chronic pain were interviewed and were asked to provide information about pain locations and their average pain intensity in the past week, and to complete measures of pain interference, psychological function and disability. Most of the participants in this sample were males (56%), Caucasian (68%), and had a cerebral palsy (34%) or muscular dystrophy (25%) problem. Most participants did not report high levels of disability (X =12.7, SD ±9.5, range 0–60) or global pain intensity (X =3.2, SD ±2.4, range 0–10). Results: Pain at more than one body site was experienced by 91% of participants. There were positive associations between pain extent with pain interference (r = 0.30) and disability (r = 0.30), and a negative association with psychological function (r = –0.38), over and above average pain intensity. Additionally, pain intensity in the back (as opposed to other locations) was associated with more pain interference (r = 0.29), whereas pain intensity in the shoulders was associated with less psychological function (r = –0.18), and pain intensity in the bottom or hips was associated with more disability (r = 0.29). Conclusion: The findings support the need to take into account pain extent in the assessment and treatment of youths with physical disabilities and chronic pain, call our attention about the need to identify potential risk factors of pain extent, and develop and evaluate the benefits of treatments that could reduce pain extent and target pain at specific sites. Keywords: pain extent, pediatric chronic pain, physical disability, function
Background
Correspondence: Jordi Miró Departament de Psicologia, Universitat Rovira i Virgili, Carretera de Valls s/n, 43007 Tarragona, Spain Telephone: +34 9 775 5179 Email [email protected]
A growing body of evidence indicates that chronic pain is a significant problem for adults with physical disabilities.1–4 Moreover, although information from pediatric populations is scarce, research indicates that chronic pain is also a relevant health issue in youth with physical disabilities.5,6 For example, recent studies have shown that pain intensity significantly and negatively impacts the physical, emotional, and social function of youth with disabilities.7–9 The experience of pain involves more than just pain intensity; pain is a multidimensional construct that has spatial (ie, the location[s] and overall extent of perceived pain), temporal (eg, constant vs intermittent, acute vs chronic), and quality (eg, hot, electrical) characteristics. Research has shown that function, at least in adults with physical disabilities, is influenced by some of these other pain characteristics over 113
submit your manuscript | www.dovepress.com
Journal of Pain Research 2017:10 113–120
Dovepress
© 2017 Miró et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php).
http://dx.doi.org/10.2147/JPR.S121590
Dovepress
Miró et al
and above the effects of pain intensity. For example, pain at certain locations, such as the head in adults with myotonic and facioscapulohumeral dystrophy10 or in the low back and legs in adults with spinal cord injury,11 has been demonstrated to be of greater importance than pain in other body locations in the function of these individuals. Similarly, pain extent – the total number of body areas where pain is experienced – has been found to be associated with function over and above the effects of global pain intensity in adult populations with physical disabilities and chronic pain.4 That is to say, adults who report more than one distinct pain problem or pain in more body locations are likely to also report poorer quality of life and worst function than those with pain in just one location, even when controlling for pain intensity. Similar findings have been reported in studies using samples of individuals with chronic pain as a primary presenting problem.12–15 However, the role that the spatial qualities of pain play in the function of youth populations with chronic pain is very limited. To the best of our knowledge, just one study with young people with chronic pain has addressed this issue. In this study, de la Vega et al7 reported a significant negative association between pain extent and sleep quality in a sample of 414 adolescents and young adults with a variety of chronic pain problems. Aili et al16 also reported an association between disturbed sleep and multi-site pain in a longitudinal study with a sample of individuals with low back pain. However, although they studied adults, their sample included individuals 20–59 years old, and so it is unclear how many of their sample were aged in their early twenties, and could therefore be regarded as young people. Although it is reasonable to hypothesize that additional research in samples of youth would replicate these very preliminary results regarding the importance of pain location and pain extent, further research to establish the reliability of the findings regarding pain site and extent in youth is needed, as children should not be viewed simply as little adults.17 In fact, investigators have called for more research to study the occurrence and impact of multi-site pain in young people, as a way to identify factors that may play a role in the impact of chronic pain in youths.12 Such information is critical in order to better understand if and how adults and youth are different with respect to the key aspects that are relevant in the function of individuals with disabilities and chronic pain. If pain extent is found to contribute to the prediction of function among youth with physical disabilities and chronic pain – particularly if it does so over and above the effects of overall pain intensity – this would help us to better understand who might be at most risk of
114
submit your manuscript | www.dovepress.com
Dovepress
worse adjustment, and therefore who might benefit the most from treatments designed to help youth with disabilities adjust to chronic pain. Furthermore, the findings from such research would also be relevant to clinicians who design specific treatment programs, and to examine and compare the results of treatments tailored to the specific needs of the patients. For example, the hypothesis that patients with chronic localized pain in the low back would respond better to physical therapy whereas those with more extended multi-site pain problems may gain the greatest benefit from cognitive behavioral therapy,18 could be tested. Given these considerations, the aim of this study was to increase our understanding of the role that pain extent plays in function among youth with disabilities and chronic pain. On the basis of previous research with adults, we hypothesized that pain extent would demonstrate a unique positive association with pain interference, and negative associations with psychological function and disability when controlling for average pain intensity. We also sought to examine the role that individual pain sites (eg, low back pain vs headache) might play in the associations between pain intensity and function, although we did not set a priori hypothesis regarding the importance of one pain site over another, given the paucity of previous research on this topic.
Methods Participants Participants came from a convenience sample of 115 young people with physical disabilities who had participated in a longitudinal study about the impact of chronic pain secondary to a physical disability. Although a number of articles have been published using data from this survey,19–22 none of the previous articles have addressed the study questions that are the focus of the current analyses. In order to participate in the original study, potential participants needed to: 1) have a chronological age from 8 to 21 years; 2) have a diagnosis of cerebral palsy, neuromuscular disease, spinal cord injury, spina bifida, or limb deficiency (acquired or congenital); 3) be able to understand and speak English; 4) have no more than mild cognitive impairment (as measured by the modified version of the Mini-Mental State Examination);23 and 5) have the capacity for expressive communication which might have included the use of augmentative communication devices. In addition, participants for the current analyses had to report that they were experiencing a bothersome pain problem (other than one associated with a minor acute injury or illness) in the 3 months prior to the interview. We did not limit participants
Journal of Pain Research 2017:10
Dovepress
to children (ie, age ≤18 years), because many pediatricians continue to treat patients that they have a history of treating, even after they become 18 years old. In fact, this study was addressed to youth, a group that normally includes individuals in their twenties.
Procedures Further details on the study procedures can be found in the original study.22 Briefly, and most germane to the current study, participants were enrolled from different sources and with different techniques including word of mouth, mailings from clinics, and contacts with a summer camp sponsored by the Muscular Dystrophy Association (USA). Written, informed consent was obtained from all participants or their legal guardian if a minor. Following study enrollment, both youth participants and one of their parents or legal guardians were interviewed in person (when possible) or via telephone. The study was approved by the Institutional Review Board at the Children’s Hospital and Regional Medical Center (Seattle, WA, USA).
Measures The parents of the youth participants in the original study were administered a structured interview that requested information about their child’s age, sex, and medical diagnosis. The youth participant interviews included questionnaires and rating scales assessing pain and disability, as well as psychological and physical functioning domains.
Pain intensity Pain intensity was measured with a 0–10 numerical rating scale (NRS-11). Participants were asked to rate their average pain intensity in the past week by choosing a single whole number between 0 (“No pain”) and 10 (“Pain as bad as could be”) that best represented that pain. The NRS-11 has been found to be valid and reliable when used with young people24 even when used with children as young as 6 years of age25,26 and with young people with physical disabilities.21
Pain site and extent The youth participants were also asked to indicate in which of 12 body location categories (that included 11 specific locations as well as an “other” category) they experienced pain as well as the intensity of the pain at each one of those locations. The 12 locations were: head, neck, chest, shoulders, back, arms, hands, bottom/hips, belly/pelvis, legs, feet, and “other”. The number of locations were summed to create the pain extent score for each participant (possible range: 1–12). Journal of Pain Research 2017:10
Pain extent and function
Pain interference We used a modified version of the Brief Pain Inventory (BPI)27,28 to assess pain interference. The modifications to the original 7-item questionnaire included: 1) adding three items that were specially relevant for this group of individuals with disabilities, and included items that assessed pain interference with “self-care (taking care of your daily needs)”, “recreational activities”, and “social activities”, thus increasing the content validity of the scale; 2) revising the interference with “walking” item to ask about interference with “mobility (ability to get around)” which made it possible for all of the participants – including those who are not able to ambulate independently – to respond to this item; and 3) the item requesting information about “normal work” was changed to request information about “school, work, or chores”, which was considered to be a more age appropriate item. Scores from the 10-item version of the BPI used in this study demonstrated excellent internal consistency, as indicated by a Cronbach’s alpha of 0.90.
Psychological functioning The 16-item Mental Health scale (MH) of the Child Health Questionnaire (CHQ-CF87) was used to assess psychological functioning.29 The CHQ–CF87 is an 87-item questionnaire that was designed to assess psychosocial and physical wellbeing in children aged between 5 and 8 years. The CHQ– CF87 is scored by first computing a raw score, and then transforming it to standardized scores, with higher scores indicating better psychological functioning. The scales in the CHQ–CF87 have demonstrated adequate psychometric characteristics in a number of samples of young people with physical and psychological diagnoses.29 Scores from the MH scale in this study demonstrated excellent internal consistency, as indicated by a Cronbach’s alpha of 0.88.
Disability Disability was assessed using the 15-item Functional Disability Inventory (FDI).30 Respondents were asked to rate how difficult it was for them to engage in regular activities in the last few days on a 0 (“No trouble”) to 4 (“Impossible”) scale.31 The FDI was developed specifically to assess disability in children, and has demonstrated excellent reliability and validity properties.30,32 Higher scores indicate more disability (possible range: 0 to 60). In the current sample, the internal consistency (Cronbach’s alpha) of the disability score was 0.81.
Statistical analyses We first computed descriptive statistics for the demographic and study variables to describe the sample. Next, submit your manuscript | www.dovepress.com
Dovepress
115
Dovepress
Miró et al
we examined the distributions of the study variables and computed variance inflation factors (VIF) for the study predictors to ensure that they met assumptions for the planned regression analyses.33 We also computed zero-order correlation coefficients between pain extent and the criterion variables. Finally, we performed three regression analyses – one for each of the criterion variables of pain interference, psychological function, and disability – to determine if pain extent and pain intensity at specific sites explained unique variance in the criterion variables. We entered average pain intensity in step 1 as a control variable. We then entered pain extent in step 2 in order to determine if it accounted for significant variance in the criterion variables, over and above pain intensity. In step 3, we entered pain intensity at each of 12 pain sites, stepwise, to determine if pain intensity at any one (or more) specific site(s) contributed to the prediction of the criterion variables when controlling for pain intensity and pain extent.
Results Sample and study variables description The majority of the study sample were White/Caucasian (68%) and males (56%). The average age of the participants when they completed the survey was 14.4 years (SD ±3.3; median 13 years; range 8–21 years). Sixteen (14%) of the participants were prepubescent (age ≤10 years), 32 (28%) were 11–12 years old, 36 (31%) were 13–15 years old, 31 (27%) were 16–18 years old, and 14 (12%) were 19–21 years old. Almost all participants experienced pain at more than one body site (91%). Additional descriptive information about the study sample and variables in the study are presented in Tables 1 and 2.
Assumptions testing All of the distributions of the study variables were adequately normal for the planned regression analyses (skewness range –1.05 to 1.46; kurtosis range, –1.07 to 1.32). In addition, all of the variance inflation factor statistics were all well below the standard cutoff value of 10 (range 1.07 to 1.42), indicating that multicollinearity would not bias the findings.33
Zero-order correlations between pain extent and pain interference, psychological functioning, and disability The zero-order associations between pain extent and the study criterion variables (pain interference, psychological functioning, and disability) were 0.47, –0.49, and 0.36 (all p
